1. Field of the Invention
This invention relates to semipermeable membrane elements of the type incorporating flat membranes, and more particularly to semipermeable membrane elements of the types, such as pressure-resistant plate type, pleated type, multiple flat tube type, spirally wound type and the like, comprising flat membranes and useful, for example, for hemofiltration or hemodialysis as so-called artificial kidneys.
2. Description of the Prior Art
Precision filtration, ultrafiltration, reverse osmosis and like processes utilizing membranes have found wide use for the separation, purification and concentration of fluids, for the production of water, and for the treatment of industrial effluents. The semipermeable membrane elements known for use in these processes are basically of the tubular type, spirally wound type, hollow fiber type and plate-and-frame type. Additionally those of the pleated type have also been proposed recently. The semipermeable membrane elements comprising flat membranes and heretofore disclosed further include those of the spirally wound type (U.S. Pat. Nos. 3,542,203, 3,554,378 and 3,746,591), the plate-and-frame type (Published Unexamined Japanese Patent Application No. 70280/1975) and the pleated type (U.S. Pat. No. 3,266,223).
With membrane elements including flat membranes and adapted for the purification of the blood, it has been considered undesirable to incorporate a spacer or like member into the channel for the blood to be treated, because when filtering the blood with an artificial kidney, for example, such a member is likely to produce a turbulent or sheared flow in the stream of blood, possibly causing hemolysis or blood coagulation.
In the course of research on such phenomena, we have unexpectedly found that a spacer of specific shape is usable without entailing hemolysis or blood coagulation, further permitting the membrane element to achieve a higher efficiency than the conventional elements including flat membranes. Based on this finding, we have accomplished the present invention.